Respiration triggers heme transfer from cytochrome c peroxidase to catalase in yeast mitochondria
Respiration triggers heme transfer from cytochrome c peroxidase to catalase in yeast mitochondria
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DOI：
10.1073/pnas.1409692111
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发表时间：
2014-12-09
影响因子：
11.1
通讯作者：
English, Ann M.
中科院分区：
文献类型：
--
作者：
Kathiresan, Meena;Martins, Dorival;English, Ann M.
在指数生长的酵母中，血红素酶，细胞色素c过氧化物酶（Ccp 1）靶向线粒体膜间隙。当可发酵来源（葡萄糖）耗尽时，细胞切换到呼吸，线粒体H2 O2水平上升。长期以来，人们一直认为CCP活性解毒线粒体H2 O2，因为这种活性在体外的效率。然而，我们发现，大量的Ccp 1退出呼吸细胞的线粒体。我们没有检测到线粒体外CCP活性，因为Ccp 1作为无血红素蛋白穿过线粒体外膜。与apoCcp 1输出平行，细胞表现出过氧化氢酶A（Cta 1），酵母中的线粒体和过氧化物酶体过氧化氢酶亚型的活性增加。这表明Cta 1可能是Ccp 1血红素的受体，这得到了Ccp 1 Delta细胞中Cta 1活性低和Ccp 1 Delta线粒体中holoCcp 1积累的支持。我们假设，Ccp 1的血红素是不稳定的过氧化氢的生产过程中的爆发细胞开始呼吸的蛋白质。为了验证这一假设，重组Ccp 1超氧化与过量的H2 O2在体外，这加速血红素转移到作为替代血红素受体添加的脱辅基肌红蛋白。此外，近端血红素铁配体，His 175，被发现是类似于85%的氧化为氧代组氨酸在extramoditrial Ccp 1从7-d细胞分离，表明血红素不稳定的结果，从这个配体的氧化。我们得出的结论是，Ccp 1通过一种先前未确定的机制对呼吸来源的H2 O2做出反应，该机制涉及H2 O2激活的血红素转移至apoCta 1。随后，Cta 1的过氧化氢酶活性，而不是CCP活性，有助于线粒体H2 O2解毒。
In exponentially growing yeast, the heme enzyme, cytochrome c peroxidase (Ccp1) is targeted to the mitochondrial intermembrane space. When the fermentable source (glucose) is depleted, cells switch to respiration and mitochondrial H2O2 levels rise. It has long been assumed that CCP activity detoxifies mitochondrial H2O2 because of the efficiency of this activity in vitro. However, we find that a large pool of Ccp1 exits the mitochondria of respiring cells. We detect no extramitochondrial CCP activity because Ccp1 crosses the outer mitochondrial membrane as the heme-free protein. In parallel with apoCcp1 export, cells exhibit increased activity of catalase A (Cta1), the mitochondrial and peroxisomal catalase isoform in yeast. This identifies Cta1 as a likely recipient of Ccp1 heme, which is supported by low Cta1 activity in ccp1 Delta cells and the accumulation of holoCcp1 in cta1 Delta mitochondria. We hypothesized that Ccp1's heme is labilized by hyper-oxidation of the protein during the burst in H2O2 production as cells begin to respire. To test this hypothesis, recombinant Ccp1 was hyper-oxidized with excess H2O2 in vitro, which accelerated heme transfer to apomyoglobin added as a surrogate heme acceptor. Furthermore, the proximal heme Fe ligand, His175, was found to be similar to 85% oxidized to oxo-histidine in extramitochondrial Ccp1 isolated from 7-d cells, indicating that heme labilization results from oxidation of this ligand. We conclude that Ccp1 responds to respiration-derived H2O2 via a previously unidentified mechanism involving H2O2-activated heme transfer to apoCta1. Subsequently, the catalase activity of Cta1, not CCP activity, contributes to mitochondrial H2O2 detoxification.